getting_started.md

Getting started

Installation and end-to-end examples

Please refer to the main README.md.

Recommended settings

The default parameters do not always gaurantee satisfying reconstructions. Regarding this, there are several things which can generally help.

Share camera parameters

If images are known to be taken with the same physical camera under identical camera settings, or images are well organized and known to be taken by several cameras, it is higly recommended to share the camera intrinsics as appropriate. To achieve this, one can set --ImageReader.single_camera_per_folder or --ImageReader.single_camera_per_image in colmap feature_extractor.

Handle high-resolution or blurry images

If images have high resolution or are blurry, it is worth trying to increase the allowed epipolar error by modifying --RelPoseEstimation.max_epipolar_error. For example, increase it to 4 or 10.

Speedup reconstruction process

Cap the number of tracks

If the number of images and points are large, the run-time of global bundle adjustment can be long. In this case, to further speed up the overall reconstruction process, the total number of points can be capped, by changing --TrackEstablishment.max_num_tracks. Typically, one image should not need more than 1000 tracks to achieve good performance, so this number can be adjusted to $1000 \times n$. Afterwards, if a full point cloud is desired (for example, to initialize a Gaussian Splatting), points can be triangulated directly by calling colmap point_triangulator.

Note, if the --skip_retriangulation is not set when calling glomap mapper, retriangulation should already been performed.

Limit optimization iterations

The number of global positioning and bundle adjustment iterations can be limited using the --GlobalPositioning.max_num_iterations and --BundleAdjustment.max_num_iterations options.